On-chip oscilloscope

ABSTRACT

A device includes a control circuit, a scope circuit, and a time-to-current converter. The control circuit is configured to receive a voltage signal from a voltage-controlled oscillator, delay the voltage signal for a delay time to generate a first control signal, and to generate a second control signal according to the first control signal and the voltage signal. The scope circuit is configured to generate a first current signal in response to the second control signal and the voltage signal. The time-to-current converter is configured generate a second current signal according to the first control signal, the voltage signal, a first switch signal, and a test control signal.

RELATED APPLICATIONS

This application is continuation of U.S. application Ser. No.16/212,090, filed Dec. 6, 2018, which is continuation of U.S.application Ser. No. 14/991,936, filed Jan. 9, 2016, now U.S. Pat. No.10,161,967, issued Dec. 25, 2018, which is herein incorporated byreference.

BACKGROUND

In an integrated circuit (IC), there are many electrical elements. Theseon-chip elements may be unable to be tested after manufacture. As such,in some applications, an on-chip oscilloscope is developed to test theelectrical elements in the chips at wafer acceptance testing (WAT)stage.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a schematic diagram of a device, in accordance with variousembodiments of the present disclosure;

FIG. 2 is a circuit diagram of the device in FIG. 1 , in accordance withvarious embodiments of the present disclosure;

FIG. 3A is a flow chart of a method illustrating operations of thedevice in FIG. 2 when the device in FIG. 2 is in a sample mode, inaccordance with various embodiments of the present disclosure;

FIG. 3B is a flow chart of a method illustrating operations of thedevice in FIG. 2 when the device in FIG. 2 is in a reset mode, inaccordance with various embodiments of the present disclosure;

FIG. 4 is a graph of waveforms illustrating operations of the device inFIG. 2 , in accordance with various embodiments of the presentdisclosure; and

FIG. 5 is a schematic diagram illustrating a voltage signalreconstructed through the device in FIG. 2 , in accordance with variousembodiments of the present disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

The terms used in this specification generally have their ordinarymeanings in the art and in the specific context where each term is used.The use of examples in this specification, including examples of anyterms discussed herein, is illustrative only, and in no way limits thescope and meaning of the disclosure or of any exemplified term.Likewise, the present disclosure is not limited to various embodimentsgiven in this specification.

Although the terms “first,” “second,” etc., may be used herein todescribe various elements, these elements should not be limited by theseterms. These terms are used to distinguish one element from another. Forexample, a first element could be termed a second element, and,similarly, a second element could be termed a first element, withoutdeparting from the scope of the embodiments. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items.

Secondly, the terms “comprise,” “comprising,” “include,” “including,”“has,” “having,” etc. used in this specification are open-ended and mean“comprises but not limited”.

In addition, the term “coupled” may also be termed as “electricallycoupled”, and the term “connected” may be termed as “electricallyconnected”. “Coupled” and “connected” may also be used to indicate thattwo or more elements cooperate or interact with each other.

FIG. 1 is a schematic diagram of a device 100, in accordance withvarious embodiments of the present disclosure. In some embodiments, thedevice 100 is applied in an on-chip oscilloscope. The device 100 isconfigured to monitor elements or internal signals in a chip.

As illustratively shown in FIG. 1 , the device 100 is configured tomonitor the voltage signal VCK. In some embodiments, the voltage signalVCK is a periodic voltage signal. For example, the voltage signal VCK isa pulse signal having a predetermined period generated from avoltage-controlled oscillator (VCO). The device 100 is configured toreceive the voltage signal VCK. The device 100 is configured to generatea current signal IW and a current signal IT, in response to the voltagesignal VCK. In some embodiments, the current signal IW is measuredthrough a current meter m1, and the current signal IT is measuredthrough another current meter m2. In some other embodiments, the currentsignals IW and IT are measured through the same current meter. In someembodiments, the current signal IW is generated to indicate theamplitude of the voltage signal VCK, and the current signal IT isgenerated to indicate time intervals of the voltage signal VCK. In otherwords, the current signal IW is associated with waveform amplitude ofthe voltage signal VCK, and the current signal IT is associated with thetime intervals of the voltage signal VCK. With such arrangement, thecurrent signal IW and the current signal IT are able to be utilized toreconstruct the voltage signal VCK.

For illustration, in some embodiments, the device 100 includes a controlcircuit 110, a scope circuit 120, and a time-to-current converter 130.The scope circuit 120 and the time-to-current converter 130 are coupledto the control circuit 110. The control circuit 110 is configured toreceive the voltage signal VCK, and to generate a control signal C1according to the voltage signal VCK. The control circuit 110 is furtherconfigured to generate a control signal C2 according to the voltagesignal VCK and the control signal C1.

Furthermore, the scope circuit 120 is configured to generate the currentsignal IW according to the control signal C2 and the voltage signal VCK.The time-to-current converter 130 is configured to generate the currentsignal IT according to the control signal C1 and the voltage signal VCK.

The device 100 in FIG. 1 is given for illustrative purposes. Variousconfigurations of the device 100 are within the contemplated scope ofthe present disclosure. For example, in some embodiments, the device 100includes two or more scope circuits 120 to achieve multiple channels.

Reference is now made to FIG. 2 . FIG. 2 is a circuit diagram of thedevice 100 in FIG. 1 , in accordance with various embodiments of thepresent disclosure. With respect to the embodiments of FIG. 1 , likeelements in FIG. 2 are designated with the same reference numbers forease of understanding.

As illustratively shown in FIG. 2 , the control circuit 110 includes adelay unit 112, an inverter 114 and an NAND gate 116. The delay unit 112has an input terminal and an output terminal. The inverter 114 has aninput terminal and an output terminal. The NAND gate 116 has a firstinput terminal, a second input terminal, and an output terminal. Theinput terminal of the delay unit 112 is configured to receive thevoltage signal VCK. The output terminal of the delay unit 112 isconfigured to output the control signal C1 to the input terminal of theinverter 114. The delay unit 112 is configured to introduce a delay timeto the voltage signal VCK to generate the control signal C1, in whichthe delay time is controlled according to a control voltage Vcon. Theoutput terminal of the inverter 114 is configured to output a controlsignal C3 to the first input terminal of the NAND gate 116. The secondinput terminal of the NAND gate 116 is configured to receive the voltagesignal VCK. The NAND gate 116 is configured to generate the controlsignal C2 according to the control signal C3 and the voltage signal VCKto the scope circuit 120.

The configuration of the control circuit 110 in FIG. 2 is given forillustrative purposes. Various configurations of the control circuit 110are within the contemplated scope of the present disclosure.

As illustratively shown in FIG. 2 , the scope circuit 120 includes atransmission gate 122, an inverter 124, a resistor R1, and a switch S1.The transmission gate 122 is coupled to the output terminal of the NANDgate 116 at a node P. The transmission gate 122 is coupled to theresistor R1 and the switch S1 at a node N. The transmission gate 122includes a switch S2 and a switch S3. The switch S2 and the switch S3are coupled in parallel with each other.

For illustration, each of the switches S1-S3 has a first terminal, asecond terminal, and a control terminal. The first terminal of theswitch S2 is coupled to the first terminal of the switch S3. The firstterminals of the switches S2-S3 are configured to receive the voltagesignal VCK. The second terminal of the switch S2 is coupled to thesecond terminal of the switch S3 at the node N. The control terminal ofthe switch S1, the control terminal of the switch S2 and an inputterminal of the inverter 124 are coupled to the output terminal of theNAND gate 116 at the node P. An output terminal of the inverter 124 iscoupled to the control terminal of the switch S3. The first terminal ofthe switch S1 is coupled to a first terminal of the resistor R1 at thenode N. The second terminal of the switch S1 is coupled to the ground. Asecond terminal of the resistor R1 is configured to output the currentsignal IW. In some embodiments, the second terminal of the resistor R1is connected to an output pad, in order to be measured through thecurrent meter m1 in FIG. 1 .

In some embodiments, the switch S2 is implemented with a P-typetransistor, and the switch S1 and the switch S3 are implemented withN-type transistors. Various types of the transistors, which are able toimplement the switches S1-S3, are within the contemplated scope of thepresent disclosure. For example, in some embodiments, the transistorsare metal-oxide-semiconductor filed-effect transistors (MOSFETs).

The configuration of the scope circuit 120 in FIG. 2 is given forillustrative purposes. Various configurations of the scope circuit 120are within the contemplated scope of the present disclosure. Forexample, in some embodiments, various types of switching circuits areable to replace the transmission gate 122 or the switch S1. In furtherembodiments, the switching circuits include a single P-type transistoror a single N-type transistor, and the transmission gate 122 is replacedby a P-type transistor or replaced by an N-type transistor.Alternatively, in some embodiments, the switch S1 is implemented byanother transmission gate or implemented by a P-type transistor.

As illustratively shown in FIG. 2 , the time-to-current converter 130has a first input terminal, a second input terminal, and an outputterminal. The first input terminal of the time-to-current converter 130is configured to receive the voltage signal VCK. The delay unit 112 isconfigured to output the control signal C1 to the second input terminalof the time-to-current converter 130. The output terminal of thetime-to-current converter 130 is configured to output the current signalIT according to the voltage signal VCK and the control signal C1. Insome embodiments, the output terminal of the time-to-current converter130 is connected to an output pad, in order to be measured through thecurrent meter m2 in FIG. 1 .

As illustratively shown in FIG. 2 , in some embodiments, thetime-to-current converter 130 includes a switch S4, a switch S5, a NANDgate 132, a NAND gate 134 and a resistor R2. In some embodiments, theswitch S4 is turned on when the switch S5 is turned off. Forillustration, the switch S4 is controlled by a switch signal SW. Theswitch S5 is controlled by a switch signal SW′. The switch signal SW′and the switch signal SW are different in phase by about 180 degrees.Each of the NAND gates 132 and 134 has a first input terminal, a secondinput terminal and an output terminal. The first input terminal of theNAND gate 132 is coupled to the switches S4 and S5. The switch S4 isconfigured to transmit the voltage signal VCK to the first inputterminal of the NAND gate 132 according to the switch signal SW. Theswitch S5 is configured to transmit the control signal C1 to the firstinput terminal of the NAND gate 132 according to the switch signal SW′.The second input terminal of the NAND gate 132 is configured to receivethe voltage signal VCK. The first input terminal of the NAND gate 134 iscoupled to the output terminal of the NAND gate 132. The second inputterminal of the NAND gate 134 is configured to receive a test controlsignal TDC. The output terminal of the NAND gate 134 is coupled to theresistor R2, and the resistor R2 is connected to the output pad, inorder to be measured through the current meter m2 in FIG. 1 . Theoperations of the time-to-current converter 130 are provided in thefollow description.

The configuration of the time-to-current converter 130 in FIG. 2 isgiven for illustrative purposes. Various configurations of thetime-to-current converter 130 are within the contemplated scope of thepresent disclosure.

In some embodiments, the device 100 in FIG. 2 is operated in a samplemode or in a reset mode according to settings of the delay unit 112. Forexample, when the device 100 is operated in the sample mode, the delayunit 112 delays the voltage signal VCK for a delay time, to generate thecontrol signal C1. Accordingly, the scope circuit 120 generates thecurrent signal IW during the delay time. A length of the delay time isadjusted depending on the control voltage Vcon. In some alternativeembodiments, when device 100 is operated in the reset mode, the delaytime is adjusted to zero. Effectively, the delay unit 112 outputs thevoltage signal VCK as the control signal C1 without introducing thedelay time. Accordingly, the scope circuit 120 stops generating thecurrent signal IW.

In order to facilitate the illustration of the operations in the samplemode, the operations of the device 100 in FIG. 2 are described withreference to both FIG. 3A and FIG. 4 below. Furthermore, in order tofacilitate the illustration of the operations in the reset mode, theoperations of the device 100 in FIG. 2 are described with reference toboth FIG. 3B and FIG. 4 below.

FIG. 3A is a flow chart of a method 300 a illustrating operations of thedevice 100 in FIG. 2 when the device 100 is operated during a sampletime T1 in FIG. 4 , in accordance with various embodiments of thepresent disclosure. FIG. 4 is a graph of waveforms illustratingoperations of the device 100 in FIG. 2 , in accordance with variousembodiments of the present disclosure. As illustratively shown in FIG. 4, in the sample time T1, the device 100 in FIG. 2 is operated in thesample mode.

For ease of understanding, in the following paragraphs, the operationsof the method 300 a are described with reference to the voltage signalVCK in FIG. 4 transiting from a logic value of 0 to a logic value of 1.As illustratively shown in FIG. 4 , in some embodiments, a voltage swingof the voltage signal VCK ranges from a voltage V1 to a voltage V2, inwhich the voltage V1 corresponds to the logic value of 0 (logicallylow), and the voltage V2 corresponds to the logic value of 1 (logicallyhigh).

Reference is now made to all of FIG. 2 , FIG. 3A, and FIG. 4 . In someembodiments, the method 300 a includes operations 311-316.

In operation 311, the delay unit 112 delays the voltage signal VCK forthe sample time T1 to generate the control signal C1. For illustration,the delay unit 112 receives the voltage signal VCK and introduces thedelay time, i.e., the sample time T1, to the voltage signal VCK inresponse to the control voltage Vcon. Since the delay unit 112 delaysthe voltage signal VCK when the voltage signal VCK transits from thelogic value of 0 to the logic value of 1, the control signal C1 stillhas the logic value of 0 in the sample time T1. Accordingly, the delayunit 112 outputs the control signal C1 having the logic value of 0 tothe inverter 114 and the time-to-current converter 130.

In operation 312, the inverter 114 inverts the control signal C1 togenerate a control signal C3. As described above, the control signal C1has the logic value of 0. Accordingly, the control signal C3 inverted bythe inverter 114 has the logic value of 1. The inverter 114 then outputsthe control signal C3 to the NAND gate 116.

In operation 313, the NAND gate 116 performs an NAND operation with thevoltage signal VCK and the control signal C3, to generate the controlsignal C2. As described above, the voltage signal VCK has the logicvalue of 1, and the control signal C3 has the logic value of 1.Accordingly, the NAND gate 116 outputs the control signal C2 having thelogic value of 0 to the scope circuit 120.

In operation 314, the transmission gate 122 is turned on by the controlsignal C2, and the switch S1 is turned off by the control signal C2. Forillustration, as described above, during the sample time T1, the controlsignal C2 has the logic value of 0. Accordingly, the switch S1 is turnedoff and the switch S2 is turned on by the control signal C2. Theinverter 124 receives and inverts the control signal C2 to generate acontrol signal C4. Since the control signal C2 has the logic value of 0,the inverter 124 outputs the control signal C4 having the logic value of1 to the control terminal of the switch S3. Thus, the switch S3 is alsoturned on.

In operation 315, the transmission gate 122 transmits the voltage signalVCK to the resistor R1 to generate the current signal IW. As describedabove, the switches S2 and S3 are turned on, the voltage signal VCK isthen transmitted through the switches S2-S3 to the node N. At the sametime, since the switch S1 is turned off, the voltage signal VCK at thenode N is transmitted through the resistor R1 to generate thecorresponding current signal IW. Since the resistance of the resistor R1is constant, the current signal IW is corresponding to an amplitude of awaveform of the voltage signal VCK. As illustratively shown in FIG. 4 ,since the voltage signal VCK is gradually transiting from the lowvoltage V1 to the high voltage V2, the current signal IW is graduallyincreased from a current I1 to a current I2 after the transmission gate122 is turned on. Therefore, the current signal IW is associated withthe amplitude of the waveform of the voltage signal VCK.

In operation 316, the time-to-current converter 130 receives the voltagesignal VCK and the control signal C1, and then generates the currentsignal IT according to the voltage signal VCK and the control signal C1.The current signal IT is corresponding to the sample time T1. In someembodiments, the time-to-current converter 130 receives the test controlsignal TDC and generates a DC current signal according to the testcontrol signal TDC. For illustration, when the test control signal TDChas the logic value of 0, an output signal of the NAND gate 134 has thelogic value of 1. Under this condition, the resistor R2 generates the DCcurrent signal. When the test control signal TDC has the logic value of1, and the voltage signal VCK and the control signal C1 are inputted tothe time-to-current converter 130, the time-to-current converter 130generates the current signal IT having a pulse during the sample timeT1. For illustration, when the switch S4 is turned on and the switch S5is turned off, the time-to-current converter 130 generates the currentsignal IT, which is referred to as a current signal IT1 hereinafter.Under this condition, the voltage signal VCK is transmitted to the firstinput terminal and the second input terminal of the NAND gate 132. TheNAND gate 132 then outputs a control signal C5 being an inverse of thevoltage signal VCK to the NAND gate 134. Since the test control signalTDC has the logic value of 1, the logic level at the output terminal ofthe NAND gate 134 is an inverse of the control signal C5. Accordingly,the logic level at the output terminal of the NAND gate 134 is same asthe logic level of the voltage signal VCK. Moreover, when the switch S4is turned off and the switch S5 is turned on, the time-to-currentconverter 130 generates the current signal IT, which is referred to as acurrent signal IT2 hereinafter. Under this condition, the control signalC1 is transmitted to the first input terminal of the NAND gate 132 andthe voltage signal VCK is transmitted to the second input terminal ofthe NAND gate 132. Since the control signal C1 is an inverse of thevoltage signal VCK during the sample time T1, the control signal C5 hasthe logic level of 1 during the sample time T1. Since the test controlsignal TDC has the logic value of 1, the logic level at the outputterminal of the NAND gate 134 has the logic level of 0 during the sampletime T1. As the current signals IT1 and IT2 are able to be measured bythe current meter m2 in FIG. 1 , the average current value of thecurrent signal IT, during the sample time T1, is able to be determinedby subtracting the current signal IT2 from the current signal IT1. Thesample time T1 is able to be derived from the following equation (1):

$\begin{matrix}{{T1} = \frac{\left( {{{IT}\; 1} - {{IT}\; 2}} \right) \times {TCK}}{Idc}} & (1)\end{matrix}$

where TCK is the period of the voltage signal VCK, and Idc is theaverage current value of the DC current signal.

The arrangement of determining the average current value Idc is givenfor illustrative purposes only. Various arrangements of determining theaverage current value Idc are within the contemplated scope of thepresent disclosure.

The above description of the method 300 a includes exemplary operations,but the operations of the method 300 a are not necessarily performed inthe order described. The order of the operations of the method 300 adisclosed in the present disclosure are able to be changed, or theoperations are able to be executed simultaneously or partiallysimultaneously as appropriate, in accordance with the spirit and scopeof various embodiments of the present disclosure.

Reference is now made to all of FIG. 2 , FIG. 3B and FIG. 4 . FIG. 3B isa flow chart of a method 300 b illustrating operations of the device 100in FIG. 2 when the device 100 is operated during a reset time T2 in FIG.4 , in accordance with various embodiments of the present disclosure. Asillustratively shown in FIG. 4 , in the reset time T2, the device 100 inFIG. 2 is operated in the reset mode. As described above, when device100 in FIG. 2 is operated in the reset mode, the delay unit 112 stopsdelaying the voltage signal VCK.

In some embodiments, the method 300 b includes operations 321-326. Inoperation 321, the delay unit 112 transmits the voltage signal VCKwithout introducing additional delay time, to generate the controlsignal C1. In other words, in the reset mode, the delay unit 112transmits the voltage signal VCK as the control signal C1 to theinverter 114. For illustration of FIG. 4 , the voltage signal VCK istransited to the logic value of 1 in a time T3. Since the delay unit 112transmits the voltage signal VCK without introducing additional delaytime, the control signal C1 also has the logic value of 1. In the timeT4, the voltage signal VCK is transiting from the voltage V2 to thevoltage V1. Accordingly, the control signal C1 also transits from thelogic value of 1 to the logic value of 0 in the time T4.

In operation 322, the inverter 114 inverts the control signal C1 togenerate the control signal C3. For illustration of FIG. 4 , in the timeT3, since the control signal C1 has the logic value of 1, the controlsignal C3 has the logic value of 0. In the time T4, since the controlsignal C1 is transiting from the logic value of 1 to the logic value of0, the control signal C3 is transiting from the logic value of 0 to thelogic value of 1.

In operation 323, the NAND gate 116 performs an NAND operation with thevoltage signal VCK and the control signal C3, to generate the controlsignal C2. For illustration of FIG. 4 , in the time T3, since thevoltage signal VCK has the logic value of 1 and the control signal C3has the logic value of 0, the control signal C2 has the logic valueof 1. In the time T4, since the voltage signal VCK is transiting to thelogic value of 0 and the control signal C3 is transiting to the logicvalue of 1, the NAND gate 116 outputs the control signal C2 having thelogic value of 1. That is, the control signal C2 has the logic value of1 in the reset time T2.

In operation 324, the transmission gate 122 is turned off by the controlsignal C2, and the switch S1 is turned on by the control signal C2. Asdescribed above, in the reset time T2, since the control signal C2 hasthe logic value of 1, the switch S1 is turned on and the switch S2 isturned off. Moreover, since the control signal C4 outputted by theinverter 124 has the logic value of 0, the switch S3 is turned off.

In operation 325, the switch S1 pulls the voltage level of the node N tothe ground. For illustration, as described above, in the sample time T1,the transmission gate 122 transmits the voltage signal VCK to the nodeN. Effectively, the voltage level of the node N is pulled up to avoltage level of the voltage signal VCK in operation 315. When thetransmission gate 122 is turned off and the switch S1 is turned on, thevoltage level of the node N is then pulled down to the ground via theswitch S1. Accordingly, the electrical signals on the resistor R1 or theswitch S1 is bypassed to the ground. Thus, there is no current flowingthrough the resistor R1. As a result, the scope circuit 120 stopsgenerating the current signal IW in the reset time T2.

The above description of the method 300 b includes exemplary operations,but the operations of the method 300 b are not necessarily performed inthe order described. The order of the operations of the method 300 bdisclosed in the present disclosure are able to be changed, or theoperations are able to be executed simultaneously or partiallysimultaneously as appropriate, in accordance with the spirit and scopeof various embodiments of the present disclosure.

FIG. 5 is a schematic diagram illustrating the voltage signal VCKreconstructed through the device 100 in FIG. 2 , in accordance withvarious embodiments of the present disclosure. For ease ofunderstanding, FIG. 5 illustrates a partial enlarged view of thewaveform of the voltage signal VCK.

Time intervals td1-td2 and the corresponding amplitudes Vswi of thevoltage signal VCK are illustrated in FIG. 5 . As illustratively shownin FIG. 5 , the time interval td1 is a time difference between a time t1and a time t2, and the time interval td2 is a time difference betweenthe time t2 and a time t3.

In some embodiments, the amplitude Vswi of the reconstructed voltagesignal VCK is derived from the equation (2) below:Vswi=(Iavi×Rr×Tck)/tdi  (2)

Where Vswi represents an average voltage value of the reconstructedvoltage signal VCK during a time interval tdi, Iavi represents anaverage current value within the time interval tdi, Rr represents aresistance of the resistor R1 in FIG. 2 , and Tck represents a period ofthe voltage signal VCK. The detailed operations to derive Iavi and tdiare described with reference to FIG. 2 .

In some embodiments, the delay unit 112 in FIG. 2 delays the voltagesignal VCK for the delay time t1 during some periods of the voltagesignal VCK. The delay time t1 is controlled according to the controlvoltage Vcon. The device 100 in FIG. 2 then performs the method 300 a inFIG. 3A, in order to generate the current signal IW and the currentsignal IT. Under this condition, the current signal IW is referred to asa current signal IW1, and the current signal IT is referred to as acurrent signal IT1. In other words, the current signal IW1 representsthe current signal IW when the delay unit 112 delays the voltage signalVCK for the delay time t1. The current signal IT1 represents the currentsignal IT when the delay unit 112 delays the voltage signal VCK for thedelay time t1. With the operation 316 of the method 300 a in FIG. 3A andthe equation (1) above, the delay time t1 is able to be determinedaccording to the current signal IT1.

Then, the delay unit 112 in FIG. 2 delays the voltage signal VCK for thedelay time t2 during other periods of the voltage signal VCK. The delaytime t2 is controlled according to the control voltage Vcon. The device100 in FIG. 2 then performs the method 300 a in FIG. 3A, in order togenerate the current signal IW and the current signal IT. Under thiscondition, the current signal IW is referred to as a current signal IW2,and the current signal IT is referred to as a current signal IT2. Inother words, the current signal IW2 represents the current signal IWwhen the delay unit 112 delays the voltage signal VCK for the delay timet2. The current signal IT2 represents the current signal IT when thedelay unit 112 delays the voltage signal VCK for the delay time t2. Withthe operation 316 of the method 300 a in FIG. 3A and the equation (1)above, the delay time t2 is able to be determined according to thecurrent signal IT2.

As the delay time t1 and the delay time t2 are determined, the timeinterval td1 is thus generated according to the delay time t1 and thedelay time t2. For example, the time interval td1 is determined bysubtracting the delay time t1 from the delay time t2. As the currentsignal IW1 and the current signal IW2 are determined, the averagecurrent value Iav1 within the time interval td1 is able to be generatedaccording to the current signal IW1 and the current signal IW2. Theaverage current value Iav1 within the time interval td1 is a differencebetween a current value of the current signal IW1 and a current value ofthe current signal IW2. For example, the average current value Iav1 isdetermined by subtracting the current signal IW1 from the current signalIW2.

Further, the delay unit 112 in FIG. 2 delays the voltage signal VCK forthe delay time t3 during other periods of the voltage signal VCK. Thedelay time t3 is controlled according to the control voltage Vcon. Thedevice 100 in FIG. 2 then performs the method 300 a in FIG. 3A, in orderto generate the current signal IW and the current signal IT. Under thiscondition, the current signal IW is referred to as a current signal IW3,and the current signal IT is referred to as a current signal IW3. Inother words, the current signal IW3 represents the current signal IWwhen the delay unit 112 delays the voltage signal VCK for the delay timet3. The current signal IT3 represents the current signal IT when thedelay unit 112 delays the voltage signal VCK for the delay time t3. Withthe operation 316 of the method 300 a in FIG. 3A and the equation (1)above, the delay time t3 is able to be determined according to thecurrent signal IT3.

As the delay time t2 and the delay time t3 are determined, the timeinterval td2 is thus generated according to the delay time t2 and thedelay time t3. For example, the time interval td2 is determined bysubtracting the delay time t2 from the delay time t3. As the currentsignal IW2 and the current signal IW3 are determined, the averagecurrent value Iav2 within the time interval td2 is able to be generatedaccording to the current signal IW2 and the current signal IW3. Theaverage current value Iav2 within the time interval td2 is a differencebetween a current value of the current signal IW2 and a current value ofthe current signal IW3. For example, the average current value Iav2 isdetermined by subtracting the current signal IW2 from the current signalIW3.

As illustratively shown in FIG. 5 , as the time intervals td1-td2 andthe corresponding amplitudes Vsw1-Vsw2 are determined, a portion of thevoltage signal VCK is reconstructed. Accordingly, by repeatedlyperforming the operations above, the voltage signal VCK is able to bereconstructed according to the equation (2).

The operations of reconstructing the voltage signal VCK in aboveembodiments are given for illustrative purposes. Various operations ofreconstructing the voltage signal VCK are within the contemplated scopeof the present disclosure.

In some embodiments, the device 100 in FIG. 2 is implemented on chipwith a small area. Thus, the device 100 is suitable for performingtesting at WAT stage and has a loading only about 10 fF, which issufficient to prevent monitored signals from distortion. Moreover, insome embodiments, the device 100 is configured to monitor internalsignals in the chip without any external oscilloscope. In variousembodiments, the device 100 is able to measure the on-chip elements atWAT stage or before a package process.

In some embodiments, the device 100 in FIG. 2 is configured to monitor apower supply voltage in an integrated circuit (IC) when the power supplyvoltage has a periodic voltage drop. In some embodiments, the device 100in FIG. 2 is configured to monitor a specific periodic waveform toobtain a rise time, a fall time or a slew rate of the specific periodicwaveform.

In this document, the term “coupled” may also be termed as “electricallycoupled,” and the term “connected” may be termed as “electricallyconnected”. “Coupled” and “connected” may also be used to indicate thattwo or more elements cooperate or interact with each other.

In some embodiments, a device includes a control circuit, a scopecircuit, and a time-to-current converter. The control circuit isconfigured to receive a voltage signal from a voltage-controlledoscillator, delay the voltage signal for a delay time to generate afirst control signal, and to generate a second control signal accordingto the first control signal and the voltage signal. The scope circuit isconfigured to generate a first current signal in response to the secondcontrol signal and the voltage signal. The time-to-current converter isconfigured generate a second current signal according to the firstcontrol signal, the voltage signal, a first switch signal, and a testcontrol signal.

Also disclosed is a device that includes a control circuit, a scopecircuit, and a time-to-current converter. The control circuit isconfigured to receive a voltage signal from a voltage-controlledoscillator, delay the voltage signal to generate a first control signal,and to generate a second control signal according to the first controlsignal and the voltage signal. The scope circuit is configured toreceive the voltage signal from the voltage-controlled oscillator and togenerate a first current signal in response to the second controlsignal. The time-to-current converter includes a NAND gate performing aNAND operation on the voltage signal and one of the voltage signal andthe first control signal to generate a third control signal. Thetime-to-current converter is further configured to generate a secondcurrent signal in response to the third control signal.

Also disclosed is a method that includes the operation below. A voltagesignal is received by a control circuit and a scope circuit from avoltage-controlled oscillator. The voltage signal is delayed by thecontrol circuit to generate a first control signal and to generate asecond control signal according to the first control signal and thevoltage signal. A first current signal is generated by the scope circuitin response to the second control signal. A NAND operation is performedon the voltage signal and one of the voltage signal and the firstcontrol signal to generate a third control signal by a NAND gate of atime-to-current converter. A second current signal is generated by thetime-to-current converter in response to the third control signal.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A device, comprising: a control circuitconfigured to receive a voltage signal from a voltage-controlledoscillator, delay the voltage signal for a delay time to generate afirst control signal, and to generate a second control signal accordingto the first control signal and the voltage signal; a scope circuitconfigured to generate a first current signal in response to the secondcontrol signal and the voltage signal; and a time-to-current converterconfigured to generate a second current signal according to the firstcontrol signal, the voltage signal, a first switch signal, and a testcontrol signal.
 2. The device of claim 1, wherein the time-to-currentconverter comprises: a first switch configured to transmit the voltagesignal according to the first switch signal; a second switch configuredto transmit the first control signal according to a second switchsignal; and a plurality of NAND gates configured to generate the secondcurrent signal according to the voltage signal, one of the voltagesignal and the first control signal, and the test control signal.
 3. Thedevice of claim 2, wherein the NAND gates comprises: a first NAND gateconfigured to perform a NAND operation on the voltage signal and one ofthe voltage signal and the first control signal to generate a thirdcontrol signal; and a second NAND gate configured to perform a NANDoperation on the third control signal and the test control signal togenerate the second current signal.
 4. The device of claim 1, wherein ina first mode, the scope circuit is configured to generate the firstcurrent signal corresponding to amplitudes of a waveform of the voltagesignal, wherein in a second mode, the scope circuit is configured tostop generating the first current signal.
 5. The device of claim 4,wherein the scope circuit comprises: a resistor; a transmission gatecontrolled by the second control signal and configured to transmit thevoltage signal to the resistor; and a switch, wherein a first terminalof the switch is coupled to the transmission gate and the resistor,wherein a second terminal of the switch is coupled to a ground, whereinin the first mode, the switch is configured to be turned off, wherein inthe second mode, the switch is configured to be turned on.
 6. The deviceof claim 1, wherein the control circuit comprises: a delay unitconfigured to delay the voltage signal to generate the first controlsignal, wherein the delay unit is controlled according to a controlvoltage.
 7. The device of claim 1, wherein the first control signal andthe second control signal are different in phase by about 180 degrees.8. A device, comprising: a control circuit configured to receive avoltage signal from a voltage-controlled oscillator, delay the voltagesignal to generate a first control signal, and to generate a secondcontrol signal according to the first control signal and the voltagesignal; a scope circuit configured to receive the voltage signal fromthe voltage-controlled oscillator and to generate a first current signalin response to the second control signal; and a time-to-currentconverter comprising a NAND gate performing a NAND operation on thevoltage signal and one of the voltage signal and the first controlsignal to generate a third control signal, wherein the time-to-currentconverter is further configured to generate a second current signal inresponse to the third control signal.
 9. The device of claim 8, whereinthe time-to-current converter further comprises: a first switch coupledto the NAND gate and configured to transmit the voltage signal to aninput terminal of the NAND gate according to a first switch signal; anda second switch coupled to the NAND gate and configured to transmit thefirst control signal to the input terminal of the NAND gate according toa second switch signal, wherein the first switch signal and the secondswitch signal are different in phase by about 180 degrees.
 10. Thedevice of claim 8, wherein the first current signal indicates anamplitude of the voltage signal, and the second current signal indicatestime intervals of the voltage signal.
 11. The device of claim 8, whereinthe control circuit comprises: a delay unit configured to delay thevoltage signal to generate the first control signal, wherein the delayunit is controlled according to a control voltage; and an inverterconfigured to invert the first control signal to generate a fourthcontrol signal.
 12. The device of claim 11, wherein the control circuitfurther comprises: a NAND gate configured to generate the second controlsignal in response to the fourth control signal and the voltage signal.13. The device of claim 8, wherein the scope circuit comprises: atransmission gate controlled by the second control signal and configuredto transmit the voltage signal; a resistor coupled to the transmissiongate at a node and configured to output the first current signal,wherein the resistor is further coupled to an output pad, in order to bemeasure through a current meter; and a first switch controlled by thesecond control signal and coupled to the node.
 14. The device of claim13, wherein in a reset mode, the first switch is configured to pull avoltage level of the node to a ground according the second controlsignal.
 15. The device of claim 13, wherein the scope circuit furthercomprises: an inverter configured to invert the second control signal togenerate a fourth control signal, wherein the transmission gate isfurther configured to be turned on according to the second controlsignal and the fourth control signal.
 16. The device of claim 13,wherein the transmission gate comprises: a second switch configured tobe turned on to transmit the voltage signal in response to the secondcontrol signal; and a third switch coupled in parallel with the secondswitch, and configured to be turned on to transmit the voltage signalaccording the second control signal.
 17. A method, comprising:receiving, by a control circuit and a scope circuit, a voltage signalfrom a voltage-controlled oscillator; delaying, by the control circuit,the voltage signal to generate a first control signal and to generate asecond control signal according to the first control signal and thevoltage signal; generating, by the scope circuit, a first current signalin response to the second control signal; performing a NAND operation,by a NAND gate of a time-to-current converter, on the voltage signal andone of the voltage signal and the first control signal to generate athird control signal; and generating, by the time-to-current converter,a second current signal in response to the third control signal.
 18. Themethod of claim 17, wherein the first current signal indicates anamplitude of the voltage signal, wherein the second current signalindicates time intervals of the voltage signal.
 19. The method of claim17, wherein delaying the voltage signal comprises: inverting the firstcontrol signal to generate a fourth control signal; and performing aNAND operation in response to the fourth control signal and the voltagesignal to generate the second control signal.
 20. The method of claim17, further comprising: pulling a voltage level associated with atransmission gate of the scope circuit to a ground according the secondcontrol signal; and stopping generating the first current signal.